In different environments there is always an accumulation of particles of various sizes. By monitoring the concentration of particles within a narrow size range using a cloud chamber, the presence of a fire, even in its earliest stags, within the monitored space may be detected. An air sample from the space being monitored is introduced into the cloud chamber after passing through a humidity chamber.
The humidification of the gas sample and cloud formation is performed with an integrated humidification/cloud chamber assembly. The main component in this assembly is the humidification/cloud chamber block. This block is machined preferably from the plastic Ertalyte, and has several advantages over prior art devices. The block contains all porting and passages between the humidification chamber and cloud chamber, and therefore minimizes connecting passage lengths. Moreover, due to the insulating qualities of Ertalyte, the block minimizes thermal gradients between the humidification chamber and the cloud chamber. This is an advantage over prior art devices since there are no external interconnecting pipes or tubing which require thermal insulation. The reduction in external "plumbing" also reduces the possibility of leaks in the system. The Ertalyte plastic is essentially inert and therefore resists scale buildup in the humidification chamber, an advantage over the aluminium humidification chamber in some prior art designs. The stability of the Ertalyte plastic also allows the cloud chamber to be directly machined in the block. This has an advantage over prior art devices that use a high quality glass or metal tubing liner to provide a stable optical path for cloud detection. This results in more parts, greater expense, and more plumbing connections.
The assembly incorporates computer controlled solenoid valves to control the flow of the fluid sample through the humidification/cloud chamber. Valve timing is readily adjustable by computer software changes to accommodate different sample flow rates, allowing for more flexibility in the selection of vacuum sources. This is an advantage over the fixed, mechanical valve timing utilized in the prior art. A further advantage of using computer controlled solenoid valves in the block assembly is the ability to vary the time between samples. By cycling the system at a slow rate until an increase in the number of condensation nuclei is detected, system water use is minimized. Reduced water use requires a smaller water reservoir, which in turn allows the entire inventive system to be placed in a smaller enclosure.
The monitor uses a microcomputer to control its operation instead of dedicated analog and/or digital circuits of the prior art. Since only a fraction of the microcomputer's capacity is used for the system's operation, complex additional tasks have been assigned to the microcomputer without having to resort to additional complex electrical circuitry. For example, the microcomputer is used to communicate the system's mechanical and electrical status as well as condensation nuclei concentration to any remote location using the EIA RS-232 communications protocol. This has the advantage of being able to transmit a large amount of information over a minimum number of supervised conductors. The microcomputer has the further advantage of continuously storing in memory a running seven day historical record of the condensation nuclei concentration for the area being protected. This produces a record "signature" of the area being protected which may be used to adjust the "alarm", "alert" or "warning" condensation nuclei concentration levels to be more in line with the base concentration levels in the area being protected.
It is therefore an object, according to the present invention, to provide a humidification and cloud chamber block which can be used for measuring the concentration of submicron particles in the air by means of a cloud chamber.
It is another object, according to the present invention, to provide a humidification and cloud chamber block which is simple in design, easy to manufacture and reliable in use.